1. Field of the Invention
The present invention relates to a robot system having a vision sensor.
2. Description of the Related Art
When applying a robot work (or task) program, prepared by an off-line teaching based on a simulation, to an actual robot, actual relative positions between the robot and objects (e.g., various peripheral equipment) present in the working environment of the robot may include errors with respect to relative positions between the corresponding models in the off-line teaching. Further, when moving an actually used robot system in position of installation, errors may arise in the relative positions between the robot and peripheral equipment during a period between before and after movement. In order to measure these errors in relative positions to, e.g., correct taught data, it is known to use a robot system having a vision sensor (also called as a “robot vision”).
In a conventional position error measurement system using a robot vision, in general, one vision-sensor set (i.e., an imaging (or image pick-up) camera and an image processing unit) is provided for one set of a robot and robot control unit. The imaging camera of the vision sensor is attached to the arm of the robot or to a work tool (i.e., an end effector) supported at the front end of the arm, and, in a state where the robot is kept stationary at desired position and orientation under the control of the robot control unit, operates to photograph an object to be measured, present in the working environment, so as to obtain image data. The image processing unit of the vision sensor connected to the robot control unit processes the image data obtained by the imaging camera, so that three-dimensional relative position and orientation between the robot and object to be measured (hereinafter referred to as a “3D relative position/orientation”) is measured.
In the above-described conventional position error measurement system, when it is desired to use a single image processing unit in common for a plurality of robots, it is necessary that, after finishing the required measurements relating to one robot, the imaging camera and the image processing unit are detached from the robot and the corresponding robot control unit, and are reconnected to another robot and another robot control unit, which should be measured subsequently. Such a reattaching work of the camera and image processing unit in association with a plurality of robots and robot control units is likely to spend time and thus to degrade working efficiency. Further, the imaging camera is generally connected through a signal cable to the image processing unit, so that the handling (e.g., detaching and connecting) of the signal cable also tends to take labor.